chapter 17: DNA test 5

Question 1

The information content of genes is in the specific sequences of ___

The DNA inherited by an organism leads to​
specific traits by dictating the ___​

Proteins are the links between ___ and ___

Gene expression, the process by which DNA directs protein synthesis, includes two stages: ___ and ___

Answer 1

nucleotides​

synthesis of proteins

genotype and phenotype​

transcription and translation​

Question 2

(The Study of Metabolic Defects Provided Evidence that Genes specify Proteins​)

In 1902, British physician Archibald Garrod first suggested that genes dictate ___ through enzymes that catalyze specific chemical reactions​

He thought symptoms of an inherited disease reflected an inability to ___

This led to one ___ hypothesis (remember…. enzymes are proteins)​

___ is current hypothesis​

Answer 2

phenotypes

synthesize a certain enzyme

gene-one enzyme

One gene-one polypeptide

Question 3

(Transcription and Translation link gene to protein (polypeptide)​

RNA is the ___ between genes and the proteins for which they code​

___ is the synthesis of RNA using information in DNA​

Transcription produces ___​

___ is the synthesis of a polypeptide (protein), using information in the mRNA​

___ are the sites of translation​

Answer 3

bridge (intermediate)

Transcription

messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA)

Translation

Ribosomes (rRNA)

Question 4

A ___ is the initial RNA transcript from any gene prior to processing​

The ___ is the concept that cells are governed by a cellular chain of command: ​
DNA → RNA → protein​

Answer 4

primary transcript

central dogma

Question 5

(Codons: Triplets of Nucleotides​)

The flow of information from gene to protein is based on a ___: a series of nonoverlapping, three-nucleotide words​

These triplets are the smallest units of uniform length that can code for an ___. ​

​

Answer 5

triplet code

amino acid

Question 6

During transcription, one of the two DNA strands, called the ___, provides a template for ordering the sequence of complementary nucleotides in an RNA transcript​

(The template strand is always the same strand​
for a given gene)​

The complementary RNA molecule is synthesized according to base-pairing rules except ___ is the complementary base to adenine (instead of thymine)​

Answer 6

template strand

uracil (U > A instead of U > T)

Question 7

During translation, the mRNA base triplets, called ___, are written in the ___ direction​

Each codon specifies the ___ (one of 20)​
to be placed at the corresponding position along​
a polypeptide

Answer 7

codons

5′ → 3′

amino acid

Question 8

Of the 64 codons, 61 code for ___; 3 codons are ___ signals to end translation​

There is ___ in the genetic code (more than one codon may specify a particular amino acid) but no ___ (no codon specifies more than one amino acid)​

The correct starting point is necessary to extract the message. This establishes the ___ (correct groupings) in order for the specified polypeptide to be produced​

Answer 8

amino acids

“stop”

redundancy

ambiguity

reading frame

Question 9

The genetic code is nearly ___, shared by the simplest bacteria to the most complex animals​

Genes can be ___ and ___ after being transplanted from one species to another​

Answer 9

universal

transcribed and translated

Question 10

(Transcription is the DNA-directed synthesis of RNA: A closer look​)

Transcription is the ___ stage of gene expression​

The RNA synthesized is complementary to the ___ template strand​

​

Answer 10

first

DNA

Question 11

(Molecular Components of Transcription​)

RNA synthesis is catalyzed by ___, which separates the DNA strands apart and joins together the ___

Like DNA polymerase RNA polymerase assembles nucleotides in the 5’- 3’ direction. ​

Unlike DNA polymerases, RNA polymerases are able to start a chain from scratch, they do not need a ___.​

Answer 11

RNA polymerase

RNA nucleotides​

primer

Question 12

The DNA sequence where RNA polymerase attaches is called the ___.​

​

The stretch of DNA that is transcribed is called a ___​

Answer 12

promoter

transcription unit

Question 13

Synthesis of an RNA Transcript

The three stages of transcription​

​

Answer 13

Initiation​

Elongation​

Termination​

Question 14

(RNA Polymerase Binding and Initiation of Transcription​)

Promoters signal the transcriptional ___​

In eukaryotes, ___ mediate the binding of RNA polymerase and the initiation of transcription​

The completed assembly of transcription factors and RNA polymerase bound to a promoter is called a ___​

A promoter called a ___ is crucial in forming the initiation complex in eukaryotes​

Answer 14

start point

transcription factors

transcription initiation complex

TATA box

Question 15

(Elongation of the RNA Strand​)

As RNA polymerase moves along the DNA, it ___ the double helix, 10 to 20 bases at a time​

Transcription progresses at a rate of ___ in eukaryotes​

A gene can be transcribed simultaneously by several RNA polymerases​

Nucleotides are added to the ___ of the​
growing RNA molecule​

Answer 15

untwists

40 nucleotides per second

3′ end

Question 16

(Eukaryotic cells modify RNA after transcription​)

Enzymes in the eukaryotic nucleus modify ___ (RNA processing) before the genetic messages are dispatched to the ___

During RNA processing, both ends (5’ and 3’) of the primary transcript are usually ___​

Answer 16

pre-mRNA

cytoplasm​

altered

Question 17

(Alteration of mRNA Ends​)

Each end of a pre-mRNA molecule is modified in a particular way​

The 5′ end receives a modified nucleotide 5′ ___

The 3′ end gets a ___

​

​

Answer 17

cap​

poly-A tail​

Question 18

(RNA Splicing​)

Most eukaryotic genes and their RNA transcripts have long noncoding stretches of nucleotides that lie between coding regions​

These noncoding regions are called intervening sequences, or ___

The other regions are called ___ because they are eventually expressed, usually translated into amino acid sequences​

___ removes introns and joins exons, creating an mRNA molecule with a continuous coding sequence​

Answer 18

introns​

exons

RNA splicing

Question 19

(Genetic information flows from mRNA to protein through the process of translation​)

A cell translates an mRNA message into protein by interpreting a series of codons along an mRNA molecule to build a ___

Transfer RNA (tRNA) transfers the ___ to ___ in a ribosome​

Translation is a complex process in terms of its biochemistry and mechanics​

Answer 19

polypeptide​

amino acids to the growing polypeptide

Question 20

(The Structure and Function of Transfer RNA​)

Molecules of tRNA are not identical​

• Each carries a specific ___ on one end​
• Each has an ___ on the other end; the anticodon base-pairs with a complementary codon on mRNA​

The anticodon pairs with a complementary codon on the mRNA​

Codon by codon, the tRNAs deposit the amino acids in the prescribed order, and the ribosome joins the amino acid into a polypeptide​

Answer 20

amino acid

anticodon

Question 21

(The Structure and Function of Transfer RNA​)

A tRNA molecule consists of a single RNA strand that is only about ___ nucleotides long​

Flattened into one plane to reveal its base pairing, a tRNA molecule looks like a ___​

Like mRNA, tRNA molecules are transcribed from ___​

Answer 21

80

cloverleaf

DNA

Question 22

Accurate translation requires two steps​

First: a correct match between a tRNA and an amino acid, done by the enzyme ___​

Second: a correct match between the tRNA anticodon and an ___

Flexible pairing at the third base of a codon is called ___ and allows some tRNAs to bind to more than one codon​

Answer 22

aminoacyl-tRNA synthetase

mRNA codon​

wobble

Question 23

(Ribosomes​)

Ribosomes facilitate specific coupling of ___ with mRNA codons in protein synthesis​

The two ribosomal subunits (large and small) are made of proteins and ___

Answer 23

tRNA anticodons

ribosomal RNA (rRNA)​

Question 24

A ribosome has three binding sites for tRNA​

The ___ site holds the tRNA that carries the growing polypeptide chain​

The ___ site holds the tRNA that carries the next amino acid to be added to the chain​

The ___ site is the exit site, where discharged tRNAs leave the ribosome​

Answer 24

P

A

E

Question 25

(Building a Polaypeptide​)

The three stages of translation​

1.

2.

3.

All three stages require protein “factors” that aid in the translation process​

Energy is required for some steps also​

Answer 25

Initiation​

Elongation​

Termination​

Question 26

(Ribosome Association and Initiation of Translation​)

___ brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits​

Answer 26

Initiation

Question 27

(Elongation of the Polypeptide Chain​)

During ___, amino acids are added one​
by one to the growing chain​

Each addition involves proteins called elongation factors and occurs in three steps: ___, ___, and ___

Translation proceeds along the mRNA in a​
5′ → 3′ direction​

Answer 27

elongation

codon recognition, peptide bond formation, and translocation​

Question 28

(Termination of Translation​)

Termination occurs when a ___ in the mRNA reaches the A site of the ribosome​

The A site accepts a protein called a ___

This reaction releases the polypeptide, and the translation assembly comes apart​

Answer 28

stop codon

release factor​

Question 29

(Targeting Polypeptides to Specific Locations​)

Two populations of ribosomes are evident in cells: ___ (in the cytosol) and ___ (attached to the ER)​

Free ribosomes synthesize proteins that function in the ___

Bound ribosomes make proteins of the ___ and proteins that are secreted from the cell​

Ribosomes are identical and can switch from free to bound​

Answer 29

free ribosomes, bound ribosomes

cytosol ​

endomembrane system

Question 30

Polypeptide synthesis always begins in the ___

Synthesis finishes in the cytosol unless the polypeptide signals the ribosome to attach to​
the ER​

Polypeptides destined for the ER or for secretion are marked by a ____

Answer 30

cytosol​

signal peptide

Question 31

(Concept 17.5: Mutations of one or a few nucleotides can affect protein structure and function​)

___ are changes in the genetic material of a cell​

___ are chemical changes in just one base pair of a gene​

The change of a single nucleotide in a DNA template strand can lead to the production of an abnormal protein​

Answer 31

Mutations

Point mutations

Question 32

Substitutions​

___ have no effect on the amino acid produced by a codon because of redundancy in the genetic code​

___ still code for an amino acid, but not the correct amino acid​

___ change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein​

Answer 32

Silent mutations

Missense mutations

Nonsense mutations

Question 33

(Insertions and Deletions​)

Insertions and deletions are additions or losses of ___ in a gene​

These mutations have a disastrous effect on the resulting protein more often than substitutions do ​

Insertion or deletion of nucleotides may alter the reading frame, producing a ___

Answer 33

nucleotide pairs

frameshift mutation​

Question 34

(New Mutations and Mutagens​)

Spontaneous mutations can occur during DNA replication, recombination, or repair​

___ are physical or chemical agents that can cause mutations​

Answer 34

Mutagens

Question 35

(What Is a Gene? Revisiting the Question​)

The idea of the gene has evolved through the history of genetics​

We have considered a gene as​

A discrete unit of inheritance ​

A region of specific nucleotide sequence in​
a chromosome​

A DNA sequence that codes for a specific polypeptide chain​